The present invention relates to a vertical axis wind turbine rotor having self-fairing vanes, and to a vane structure for such a turbine rotor, improving upon the wind turbine rotor and vane disclosed in the Barnard, U.S. Pat. No. 4,681,512, issued Jul. 21, 1987.
Referring to attached FIG. 1, Barnard discloses a wind turbine having a vertical shaft 2 and a mounting hub 4. The hub 4 is journalled for rotation in a selected direction of rotation R around the vertical longitudinal axis of the shaft. The hub 4 can be journalled on a base, on the shaft 2, or it can be fixedly attached to the shaft 2 and the shaft journalled on a base. A plurality of vanes 10a, 10b, 10c, 10d are disposed quadrantly on the hub 4. The vanes 10a, 10b, 10c, 10d each comprise a frame 12 and a flexible resilient sail 14 secured to the frame. The frame 12 of each of the vanes 10a, 10b, 10c, 10d is semi-elliptical in shape, and the sail 14 when full has the shape of a generally cylindrical segment defined by the two planes, one perpendicular to the axis of the cylinder and one at forty-five degrees (45.degree.) to the axis, which intersect along the minor axis of the semi-elliptical frame and a diameter of the cylinder. As the hub 4 rotates in the selected direction of rotation R, the respective instantaneous direction of movement of each vane 10a, 10b, 10c, 10d around the axis of the shaft is shown by A, B, C, D. The wind direction is indicated by the arrow W, and numerals 24 and 26 respectively designate the head edge and the foot edge of the sail of a vane.
In the Barnard wind turbine rotor, the sail of each vane is in succession filled when being driven downwind, causing rotation of the hub or hub and shaft, thereby converting wind energy to rotation of structure. A power take-off can be operatively connected to the hub or shaft for performing work, i.e. driving a load. As each sail is, in turn, being driven upwind as the turbine rotor rotates, that sail becomes temporarily faired, i.e., it streams behind the respective vane frame, for diminishing drag. In Bamard, the vane frame shape said to be preferred is a semi-ellipse, i.e. one-half of the intersection of a plane cutting a right circular cylinder at a 45-degree angle to the longitudinal axis of the cylinder.
In the Barnard construction, the center of pressure of each of the vanes 10a, b, c, d is higher than the center of hub 4, thereby creating a rotational moment in the vertical plane through the hub, which applicant submits would contribute to excessive wear of the bearing mechanism (not illustrated) on which the hub 4 is journalled.